Since it came up in another thread, I went and installed the VBHTMLMaker from here. It seems to work just fine although I'm not wild about some of the code (but my fingers itch when I read almost anyone else's source code, so that's not unusual). A bit more excitement in the colouring department wouldn't go amiss, but that's nitpicking.
Option Explicit
Public Function AddDate(interval As String, increment As Long, fromDate As Date) As Date
' make DateAdd available to the worksheet
On Error GoTo Catch
If UCase(Left(interval, 1)) = "Y" Then
interval = "yyyy"
End If
AddDate = DateAdd(interval, increment, fromDate)
Finally:
On Error GoTo 0
Exit Function
Catch:
Resume Finally
End Function